Microwave IC package

ABSTRACT

A surface mountable microwave IC package includes a dielectric substrate; a ground conductor disposed on a front surface of a dielectric substrate on which a microwave IC chip is disposed and grounded; and a transmission line for connecting the microwave IC chip to a coplanar line on a package substrate outside the microwave IC package. The upper coplanar line is disposed on the front surface of the dielectric substrate and includes the ground conductor on which the IC chip is disposed. The lower coplanar line is disposed on the rear surface of the dielectric substrate. The intermediate coplanar line penetrates through the dielectric substrate and connects the upper coplanar line to the lower coplanar line. Therefore, the microwave transmission path from the package substrate to the IC chip is a coplanar transmission line so that a continuous transmission mode is maintained through the microwave transmission path. As a result, reflection of high frequency signals caused by the mismatching of characteristic impedances in the microwave transmission line is significantly reduced.

FIELD OF THE INVENTION

The present invention relates to microwave IC packages and, moreparticularly, to surface mountable microwave IC packages including highfrequency signal transmission lines.

BACKGROUND OF THE INVENTION

Generally, a semiconductor device is fabricated by sealing asemiconductor IC chip in a prescribed package and mounting the packageon a package substrate. There are various kinds of packages according tothe respective uses and kinds of IC chips included therein.

FIG. 9(a) is a perspective view illustrating a general-purpose plasticmolded package a an example of the above-described semiconductor ICpackages. In FIG. 9(a), reference numeral 700 designates the plasticmolded package. A semiconductor IC chip 3 is disposed on a die pad of alead frame, and electrode pads of the IC chip 3 are connected to leadterminals of the lead frame by bonding wires or the like. Then, the ICchip 3 on the lead frame is encapsulated in a molded plastic 701, andexternal lead terminals 702 are downwardly bent with respect to theplane surface of the lead frame on which the chip 3 is disposed. Theexternal lead terminals 702 thus bent serve as lead pins for connectingthe package 700 to a package substrate.

A method of mounting the plastic molded package 700 on the packagesubstrate will be described. Initially, a printed circuit board (notshown) is prepared. A conductive layer having a prescribed wiringpattern is printed on the rear surface of the board and holes for thelead pins 702 of the package 700 are formed through the board. Then, endportions 702a of the lead pins 702 are inserted in the through-holesfrom the surface side of the printed circuit board and connected to theconductive layer on the rear surface of the board by solder or the like.

In the above-described method for mounting the conventional package 700,however, since the lead pins 702 of the package are connected to theconductive layer on the rear surface of the printed circuit board, thepackage is mounted on only one side of the printed circuit board so thathigh-density mounting is not achieved.

In order to solve this problem, surface mountable packages have beenused in recent years. FIG. 9(b) is a perspective view illustrating theconventional surface mountable package disclosed in Japanese PublishedPatent Application No. 4-25036. In FIG. 9(b), reference numeral 600designates the surface mountable package. Lead pins 602 are bent so thatend portions 602a are level with the rear surface of the plastic package601. When the package is mounted on a package substrate, the endportions 602a are put on a conductive layer on the surface of thepackage substrate and adhered to the conductive layer by solder or thelike, whereby the lead pins and the wiring on the package substrate areconnected to each other on the surface of the package substrate whereonthe package is mounted. That is, packages can be mounted on bothsurfaces of the package substrate.

In addition, the surface mountable package 600 can be filled with a highfrequency semiconductor IC chip (hereinafter referred to as microwave ICchip) using the lead pins 602 appropriately as grounding pins or signalpins. In this case, however, since the lead pins 602 are merely wires,the line inductance of each lead pin significantly increases in a highfrequency band, thereby deteriorating performance of the microwave ICchip. In order to solve the problem in the high frequency band, there isa microwave IC package in which a coplanar line including a groundinglead pin and a signal lead pin which are connected to a groundingterminal and a signal terminal of the IC chip by bonding wires,respectively. The above-described Japanese Published Patent ApplicationNo. 4-25036 also discloses a microwave IC package of this kind.

In the above-described surface mountable package, however, the moldedplastic having a certain dielectric constant is closely adhered to themicrowave IC chip, so that characteristics of the IC chip in the designstage are unfavorably changed or deteriorated due to the molded plastic.In addition, the lead frame and the IC chip are encapsulated together inthe molded plastic after the die bonding and the wire bonding areperformed, so that the packaging is complicated. Therefore, it isdifficult to provide a plurality of IC packages including differentfunction IC chips in a short time in compliance with the requests of theuser.

In order to solve the above-described problems, an improved surfacemountable package has been developed, which can complete the packagingby only disposing a microwave IC chip on a package body and putting alid thereon. This package avoids deterioration in the characteristics ofthe microwave IC chip and promptly meets the user's demand.

FIGS. 10, 11(a)-11(c), and 12(a)-12(b) are diagrams for explaining theimproved surface mountable microwave IC package. More specifically, FIG.10 is a perspective view, partly broken away, illustrating the externalappearance and the internal structure of the package. FIG. 11(a) is abottom view of the package, FIG. 11(b) is a side elevational viewthereof, and FIG. 11(c) is a cross-sectional view taken along a lineXIc--XIc of FIG. 11(a). FIGS. 12(a) and 12(b) are a perspective view anda front elevational view, respectively, for explaining a method ofmounting the package on a package substrate.

In these figures, a surface mountable package 500 comprises a packagebody 501 on which a microwave IC chip 1 is disposed and a lid 590 put onthe package body 501.

The package body 501 comprises a ceramic substrate 501a and a groundconductor layer 501b. Portions of the ground conductor layer 501b areselectively removed to form U-shaped gaps 502a and 502b, whereby aninput side coplanar transmission line part 550 and an output sidecoplanar transmission line part 560 are formed, respectively.

More specifically, a portion 552 of the conductor layer 501b surroundedby the U-shaped gap 502a serves as a coplanar signal conductor of theinput side coplanar transmission line part 550, and portions 551 and 553of the conductor layer 501b serve as ground conductors. Similarly, aportion 562 of the conductor layer 501b surrounded by the U-shaped gap502b serves as a coplanar signal conductor of the output side coplanartransmission line part 560, and portions 561 and 563 of the conductorlayer 501b serve as ground conductors. As shown in FIG. 11(b), a width Wof the coplanar signal conductor 552 (562) and intervals G between thesignal conductor 552 (562) and the ground conductors 551 and 553 (561and 563) are chosen so that characteristic impedance of the coplanartransmission line part 550 (560) is 50Ω.

The input side signal conductor 552 and the output side signal conductor562 are connected to an input side signal lead 512 and an output sidesignal lead 522, respectively. The input side ground conductors 551 and553 and the output side ground conductors 561 and 563 are connected toinput side ground leads 511 and 513 and output side ground leads 521 and523. An input terminal 510 comprises the leads 511 to 513 and an outputterminal 520 comprises the leads 521 to 523. When the package is mountedon a package substrate 601, the input and output terminals 510 and 520are connected to coplanar transmission lines 610 and 620 on the packagesubstrate, respectively.

Meanwhile, on the surface of the ceramic substrate 501a, conductorlayers 503a and 503b are disposed at positions opposite to the coplanarsignal conductors 552 and 562, respectively. The conductor layer 503aserves as a strip signal conductor of the input side microstriptransmission line part 570, and portions of the ceramic substrate 501aopposite to the portions 551 and 553 of the ground conductor layer 501bserve as ground conductors of the input side microstrip transmissionline part 570. Similarly, the conductor layer 503b serves as a stripsignal conductor of the output side microstrip transmission line part580, and portions of the ceramic substrate 501a opposite to the portions561 and 563 of the ground conductor layer 501b serve as groundconductors of the output side microstrip transmission line part 580. Thewidth of the strip signal conductor 503a (503b) and the thickness and adielectric constant of the ceramic substrate 501a are appropriatelychosen so that the characteristic impedance of the microstriptransmission line part 570 (580) is 50Ω. In addition, the strip signalconductors 503a and 503b on the surface of the ceramic substrate 501aare connected to the coplanar transmission lines 552 and 562 on the rearsurface of the ceramic substrate via through-holes 504a and 504b filledwith a conductive material, respectively.

Through-holes 505 filled with a conductive material are located in aregion of the ceramic substrate 501a where the microwave IC chip 1 isdisposed. When the IC chip 1 is disposed on the region of the ceramicsubstrate 501a, a ground conductor film 1a of the IC chip 1 is connectedto the ground conductor layer 501b on the rear surface of the packagevia the through-holes 505.

A description is given of a method for mounting the microwave IC packageon the package substrate.

Initially, the microwave IC chip 1 is adhered to the package body 501with a conductive adhesive or the like, and input and output sideelectrode pads (not shown) on the surface of the chip 1 are connected tothe input and output side strip signal conductors 503a and 503b bybonding wires 2a and 2b, respectively. Then, the lid 590 is put on thepackage body 501 and adhered to the package body with an adhesive or thelike. The lid 590 provides both a hermetic seal and shielding.

Then, as illustrated in FIG. 12(a), the microwave IC package 500 ismounted on the package substrate 601. On the package substrate 601, aredisposed a coplanar transmission line 610 for applying microwave signalsto the microwave IC chip 1 and a coplanar transmission line 620 fortransferring microwave signals from the IC chip 1 to the subsequentstage. The coplanar transmission lines 610 and 620 are connected to theinput terminal 510 and the output terminal 520 of the package 500,respectively.

More specifically, when the microwave IC package 500 is put at aprescribed position of the package substrate 601, the signal lead 512 ofthe input terminal 510 contacts the signal conductor 612 of the coplanartransmission line 610 while the signal lead 522 of the terminal 520contacts signal conductor 622 of the coplanar transmission line part620. The ground leads 511 and 513 of the input terminal 510 contact theground conductors 611 and 613 of the coplanar transmission line 610while the ground leads 521 and 523 of the output terminal 520 contactthe ground conductors 621 and 623 of the coplanar transmission line 620.Then, the respective contacting parts are fixed by solder or the like,whereby the microwave IC package 500 is mounted on the package substrate601.

Then, another microwave IC package 500 is mounted on the rear surface ofthe package substrate 601 in the same manner as described above (FIG.12(b)). In this way, microwave IC packages 500 are mounted on bothsurfaces of the package substrate 601, resulting in a high-densitymounting hybrid IC.

Japanese Published Patent Application No. 2-106707 discloses a hybrid ICin which an end of a microstrip line on a package substrate is used as aterminal for an I/O interface with an external circuit.

In the microwave IC package 500 thus mounted on the package substrate601, a microwave input applied to the input terminal 510 from the signalsupply side coplanar line 610 travels through the input side coplanartransmission line part 550 on the rear surface of the package body andthe through-hole 504a and reaches the input side microstrip transmissionline part 570 on the surface of the package body. Then, the microwavesignal travels through the bonding wire 2a to reach the microwave ICchip 1.

Thereafter, the microwave signal is subjected to a prescribed signalprocessing, for example, amplification, switching, phase modification,or the like according to the function of the IC chip, and then it isoutput from the IC chip 1. The microwave signal output travels throughthe bonding wire 2b, the output side microstrip transmission line part580, and the through-hole 504b to reach the output side coplanartransmission line part 560. Then, it is output to the signal transferside coplanar line 620 on the package substrate 601 from the outputterminal 520 of the package 500.

In the prior art surface mountable microwave IC package 500, the stripsignal conductors 503a and 503b disposed on the surface of the ceramicsubstrate 501a are connected to the coplanar signal conductors 552 and562 on the rear surface of the ceramic substrate 501a by thethrough-holes 504a and 504b which are filled with conductive material.However, the through-holes merely connect these signal conductors of themicrowave transmission lines on the opposite surfaces of the ceramicsubstrate, and a microwave transmission line comprising the signalconductor and the ground conductors having a matched characteristicimpedance is not achieved. That is, the through-holes 504a and 504bcause discontinuities in the microwave transmission lines from the inputand output terminals 510 and 520 to the microwave IC chip 1,respectively, and mismatching of characteristic impedances occursbetween the through-hole and the transmission line before or behind thethrough-hole, with the result that reflection of the microwave signalunfavorably increases.

Meanwhile, Japanese Published Patent Application No. 2-156702 disclosesanother microwave IC package provided with input and output side striplines comprising ground conductor layers disposed on the surface of adielectric substrate and strip conductors disposed on the rear surfaceof the substrate, in place of the input and output side coplanartransmission parts 550 and 560 and the input and output side microstriptransmission parts 570 and 580 of the microwave IC package describedwith respect to FIGS. 10˜12. Also in this IC package, the stripconductors on the rear surface of the dielectric substrate are connectedto the microwave IC chip by through-holes penetrating the dielectricsubstrate, so that the through-holes cause discontinuities in thetransmission lines, whereby mismatching of characteristic impedancesoccurs between the through-hole and the transmission line before orafter the through-hole.

Furthermore, Japanese Published Patent Application No. 4-38855 disclosesanother microwave IC package in which a microwave IC chip is disposed ona package body and dielectric films whereon coplanar lines are formedare provided as input and output terminals of the package. In thisstructure, a continuous transmission mode is obtained through themicrowave transmission line from the transmission line on the packagesubstrate to the microwave IC chip, but the connection between thecoplanar line on the dielectric film and the coplanar line on thepackage substrate is not easily made by solder or the like because thedielectric film should be pressed onto the package substrate by pressuremeans.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a microwave ICpackage in which a transmission line on the rear surface of a dielectricsubstrate is connected to a transmission line on the front surface ofthe substrate while maintaining a continuous transmission mode betweenthe transmission lines and which is easily mounted on a packagesubstrate with solder or the like.

Other objects and advantages of the present invention will becomeapparent from the detailed description given hereinafter; it should beunderstood, however, that the detailed description and specificembodiment are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

According to a first aspect of the present invention, in a microwave ICpackage, a substrate on which a microwave IC chip is to be disposedcomprises a dielectric substrate body, a ground conductor disposed on asurface of the dielectric substrate, whereon a microwave IC chip isdisposed and grounded, and a transmission line for connecting themicrowave IC chip to a coplanar line on a package substrate outside themicrowave IC package. The transmission line has a coplanar linestructure comprising a signal conductor and a ground conductor, and itcomprises upper, lower, and intermediate coplanar lines. The uppercoplanar line is disposed on the surface of the dielectric substrate andincludes a ground conductor which is a part of the ground conductor onwhich the IC chip is disposed. The lower coplanar line is disposed onthe rear surface of the dielectric substrate so that it can be connectedto the coplanar line on the package substrate. The intermediate coplanarline penetrates through the dielectric substrate and connects the uppercoplanar line to the lower coplanar line. Therefore, the microwavetransmission path from the package substrate outside the package to themicrowave IC chip inside the package includes a coplanar transmissionline, so that a continuous transmission mode is maintained through thepath from the package substrate to the microwave IC. As the result,reflection of high frequency signals caused by the mismatching ofcharacteristic impedances in the microwave transmission line issignificantly reduced.

In addition, since the lower coplanar line that can be connected to thecoplanar line on the package substrate is present on the rear surface ofthe package body, the microwave IC package is easily mounted on thepackage substrate by solder or the like.

According to a second aspect of the present invention, the substrate onwhich the microwave IC chip is to be disposed is fabricated in thefollowing process steps. Initially, a metal plate is prepared as aconductive transmission line for connecting the IC package to thepackage substrate. The metal plate includes an H-shaped part, upper andlower I-shaped parts which are disposed between opposite side portionsof the H-shaped part and parallel with the opposite side portions, upperconnecting parts for connecting an upper end of the upper I-shaped partto upper ends of the H-shaped part, and lower connecting parts forconnecting a lower end of the lower I-shaped part to lower ends of theH-shaped part. Then, the metal plate is downwardly bent at a right anglewith respect to the plane surface of the metal plate, along two firstlines running parallel to a horizontal portion of the H-shaped part andopposite to each other with the horizontal portion between, whereby theupper coplanar line is formed. Then, the metal plate is again bent at aright angle along two second lines running parallel to the horizontalportion of the H-shaped part and opposite to each other with thehorizontal portion between so that bent portions may be parallel to theplane surface of the metal plate, whereby the intermediate coplanar lineand the lower coplanar line are formed. Accordingly, the metal plate ispartially encapsulated in a molded plastic so that the surface of theupper coplanar line where the IC chip is to be disposed and the rearsurface of the lower coplanar line which is to be connected to thepackage substrate are exposed. Finally, the upper and lower connectingportions are removed. Therefore, the substrate for the IC chip is easilyformed by machining and plastic molding.

According to a third aspect of the present invention, in the surfacemountable microwave IC package, a radiating heat sink is disposed on therear surface of the ground conductor on which the IC chip is disposed.Therefore, heat generated in the microwave IC chip is effectivelyradiated through the heat sink.

According to a fourth aspect of the present invention, in the surfacemountable microwave IC package, the metal plate includes flanges formedat both ends of the upper plane part of the bent metal plate, and thereare holes through the flanges, whereby a lid for shielding the microwaveIC chip can be fastened to the flanges with bolts and nuts through theholes. Therefore, the packaging of the microwave IC chip is simplified.

According to a fifth aspect of the present invention, in a surfacemountable microwave IC package, a substrate on which a microwave IC chipis to be disposed comprises a conductive substrate whereon a microwaveIC chip is disposed and grounded and a transmission line for connectingthe microwave IC chip to a microstrip line on a package substrateoutside the microwave IC package. The transmission line has a microstripline structure, in which a strip signal conductor is disposed opposite aground conductor on a dielectric substrate, and comprises upper, lower,and intermediate microstrip lines. The upper microstrip line is disposedon the surface of the conductive substrate where the microwave IC chipis disposed. The lower microstrip line is disposed adjacent to theconductive substrate so that the rear surface thereof may be level withthe rear surface of the conductive substrate. The intermediatemicrostrip line is disposed on the side of the conductive substrate andconnects the upper microstrip line to said lower microstrip line.Therefore, the microwave transmission path from the package substrateoutside the package to the microwave IC chip inside the package is themicrostrip transmission line, so that a continuous transmission mode ismaintained through the path from the package substrate to the microwaveIC. As the result, reflection of high frequency signals caused by themismatching of characteristic impedances in the microwave transmissionline is significantly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) and 1(b) are perspective views illustrating a microwave ICpackage in accordance with a first embodiment of the present invention;

FIG. 2 is a perspective view illustrating a method of mounting themicrowave IC package on a package substrate;

FIGS. 3(a)-3(c) are perspective views illustrating a method of forming acoplanar transmission line part included in a package body;

FIGS. 4(a) and 4(b) are perspective views illustrating a method offorming a dielectric substrate package body and a method of packagingthe microwave IC chip, respectively;

FIG. 5 is a perspective view illustrating a structure of a microwave ICpackage in accordance with a second embodiment of the present invention;

FIG. 6 is a perspective view illustrating a structure of a microwave ICpackage in accordance with a third embodiment of the present invention;

FIG. 7 is a perspective view illustrating an external appearance of amicrowave IC package in accordance with a fourth embodiment of thepresent invention;

FIG. 8 is a perspective view illustrating a method of mounting thepackage of FIG. 7 on a package substrate;

FIGS. 9(a) and 9(b) are perspective views illustrating a plastic moldedpackage and a surface mountable package, respectively, in accordancewith the prior art;

FIG. 10 is a perspective view, partly broken away, illustrating asurface mountable microwave IC package according to the prior art;

FIGS. 11(a)-11(c) are diagrams illustrating the surface mountablemicrowave IC package of FIG. 10, in which FIG. 11(a) is a bottom view,FIG. 11(b) is a side elevational view, and FIG. 11(c) is across-sectional view taken along a line XIc--XIc of FIG. 11(a); and

FIGS. 12(a) and 12(b) are a perspective view and a front elevationalview, respectively, for explaining a method of mounting the surfacemountable microwave IC package of FIG. 10 on a package substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1(a) and 1(b) are perspective views illustrating a microwave ICpackage in accordance with a first embodiment of the present invention,in which FIG. 1(a) shows the external appearance and the internalstructure of the package and FIG. 1(b) shows the structure of aconductor included in the package. FIG. 2 is a perspective viewillustrating a method of mounting the microwave IC package on a packagesubstrate. FIGS. 3(a)-3(c) are perspective views illustrating a methodof producing the conductor of FIG. 1(b). FIGS. 4(a) and 4(b) areperspective views illustrating a method of packaging the microwave ICchip.

In these figures, the surface mountable microwave IC package 101comprises a package body 110a on which a microwave IC chip 1 is to bedisposed and a lid 120 put on the package body 110a. The lid 120provides both a hermetic seal and shielding.

The package body 110a comprises a dielectric substrate 110, a groundconductor 100a on which the microwave IC chip 1 is mounted and grounded,and input side and output side transmission lines 10 and 20. The chip 1is connected to input and output coplanar lines 210 and 220 on a packagesubstrate 201 through the transmission lines 10 and 20, respectively.Each transmission line has a conventional coplanar line structure inwhich coplanar signal and ground conductors are disposed on the sameplane of the dielectric substrate.

The input side transmission line 10 comprises an upper coplanartransmission line part 10c, a lower coplanar transmission line part 10a,and an intermediate coplanar transmission line part 10b. Morespecifically, the upper coplanar transmission line part 10c is disposedon the front surface of the dielectric substrate 110 and connected tothe microwave IC chip 1. The lower coplanar transmission line part 10ais disposed on the rear surface of the dielectric substrate 110 so thatit can be connected to the input side coplanar line 210 on the packagesubstrate 201. The intermediate coplanar transmission line part 10bpenetrates through the dielectric substrate 110 and connects the uppercoplanar transmission line part 10c to the lower coplanar transmissionline part 10a. The coplanar transmission parts 10a to 10c comprisecoplanar signal conductors 12a to 12c and ground conductors 11a to 11cand 13a to 13c, respectively.

In addition, the output side transmission line 20 comprises an uppercoplanar transmission line part 20c, a lower coplanar transmission linepart 20a, and an intermediate coplanar transmission line part 20b. Morespecifically, the upper coplanar transmission line part 20c is disposedon the front surface of the dielectric substrate 110 and connected tothe microwave IC chip 1. The lower coplanar transmission line part 20ais disposed on the rear surface of the dielectric substrate 110 so thatit can be connected to the output side coplanar line 220 on the packagesubstrate 201. The intermediate coplanar transmission line part 20bpenetrates through the dielectric substrate 110 and connects the uppercoplanar transmission line part 20c to the lower coplanar transmissionline part 20a. The coplanar transmission parts 20a to 20c comprisecoplanar signal conductors 22a to 22c and grounding conductors 21a to21c and 23a to 23c, respectively.

A description is given of a method of forming the microwave IC package.

Initially, a metal plate 100 shown in FIG. 3(a) is prepared. This metalplate 100 comprises an H-shaped part 100b, an upper I-shaped part 22between upper portions 21 and 23 of the H-shaped part 100b, a lowerI-shaped part 12 between lower portions 11 and 13 of the H-shaped part100b, upper connecting parts 24 connecting an upper end of the I-shapedpart 22 to upper ends of the portions 21 and 23, and lower connectingparts 24 connecting a lower end of the I-shaped part 12 and lower endsof the portions 11 and 13.

Then, as illustrated in FIG. 3(b), the metal plate 100 is downwardlybent at right angles with respect to the plane surface of the metalplate 100 along dashed lines P1 of FIG. 3(a) to form the signalconductors 12c and 22c and the ground conductors 11c, 13c, 21c, and 23cof the upper coplanar transmission parts 10c and 20c.

Then, as illustrated in FIG. 3(c), the metal plate 100 is again bent atright angles along dashed lines P2 of FIG. 3(b) so that bent portionsare parallel to the planar front surface of the metal plate, to form thesignal conductors 12b and 22b and the ground conductors 11b, 13b, 21b,and 23b of the intermediate coplanar transmission parts 10b and 20b andthe signal conductors 12a and 22a and the ground conductors 11a, 13a,21a, and 23a of the lower coplanar line parts 10a and 20a.

Then, the processed metal plate 100 is partially encapsulated in amolded plastic to form the dielectric substrate 110 as shown in FIG. 4.More specifically, the molding should be carried out so that thesurfaces of the ground conductor 100a and the upper coplanartransmission parts 10c and 20c are level with the front surface of thedielectric substrate 110, and the rear surfaces of the lower coplanartransmission parts 10a and 20a are level with the rear surface of thedielectric substrate 110.

After the connecting portions 14 and 24 are removed, the microwave ICchip 1 is bonded to the ground conductor 100a, and electrode pads of thechip 1 are connected to the signal conductors 12c and 22c of the inputand output side upper coplanar transmission parts 10c and 20c by metalwires 2a and 2b comprising Au or the like, respectively. Then, the lid12 is put on the package body 110 to cover the IC chip 1 and adhered tothe package body 110 with solder or the like (FIG. 4(b)). Thus, asurface mountable microwave IC package is achieved.

A Kovar plate or the like onto which Au is plated to a thickness ofabout several microns is used as the metal plate 100. In addition, thecharacteristic impedance of each coplanar transmission line part isdetermined by the interval G1 between the ground conductor and thecoplanar signal conductor, the width W1 of the signal conductor, and thedielectric constant εr of the dielectric substrate. For example, whenthe dielectric substrate is formed of an epoxy resin having a dielectricconstant εr =4 and the thickness of the substrate is 0.5 mm, acharacteristic impedance of 50Ω is obtained by setting the interval G1to 100 microns and the width W1 to 760 microns.

Although epoxy resin is used as a material of the dielectric substratein the above-described first embodiment, glass or ceramic may be used.In the case of using glass or ceramic, transfer molding or sintering ispreferably employed to form the dielectric substrate.

A method of mounting the microwave IC package 101 on the packagesubstrate 201 will be described. The microwave IC package 101 is put onthe substrate 201 so that the signal conductor 12a and the groundconductors 11a and 13a of the input side lower coplanar transmissionline part 10a may be laid on the signal conductor 212 and the groundconductors 211 and 213 of the signal supply side coplanar line 210 ofthe package substrate 201, respectively, and the signal conductor 22aand the ground conductors 21a and 23a of the output side lower coplanartransmission line part 20a may be laid on the signal conductor 222 andthe ground conductors 221 and 223 of the signal transfer side coplanarline 220, respectively. Then, the respective contacting parts are fixedwith solder or the like, whereby the microwave IC package 101 is mountedon the package substrate 201.

In operation, a microwave signal input is transferred to the lowercoplanar transmission line part 10a serving as an input terminal fromthe signal supply side coplanar line 210. The microwave signal travelsthrough the lower coplanar transmission line part 10a, the intermediatecoplanar transmission line part 10b, the upper coplanar transmissionline part 10c, and the bonding wire 2a to reach the microwave IC chip 1.

In the IC chip 1, the microwave signal is subjected to a prescribedsignal processing, such as amplification, switching, phase modulation,or the like according to the function of the IC chip 1 and then it isoutput from, the IC chip 1. Then, the microwave signal output travelsthrough the bonding wire 2b, the upper coplanar transmission line part20c, and the intermediate coplanar transmission line part 20b to reachthe lower coplanar transmission line part 20a. Then, it is output to thesignal transfer side coplanar line 220 on the package substrate 201.

According to the first embodiment of the present invention, the inputand output side coplanar transmission parts 10c and 20c on the frontsurface of the dielectric substrate 110 are connected to the input andoutput side coplanar transmission parts 10a and 20a on the rear surfaceof the dielectric substrate 110 by the intermediate coplanartransmission parts 10b and 20b penetrating through the dielectricsubstrate 110. Therefore, the microwave transmission path from thepackage substrate 201 outside the package 101 to the microwave IC chip 1inside the package 101 is a coplanar transmission line, so that acontinuous transmission mode is maintained through the path from thepackage substrate 201 to the microwave IC. As the result, reflection ofhigh frequency signals caused by the mismatching of characteristicimpedances in the microwave transmission line is significantly reduced.

FIG. 5 is a perspective view for explaining an microwave IC package inaccordance with a second embodiment of the present invention. In thisembodiment, a radiating heat sink 112 is disposed beneath the groundconductor 100a on which an IC chip is to be disposed. Other structuresare the same as those in the above-described first embodiment.

More specifically, the heat sink 112 comprising an alloy of copper andtungsten, Kovar, or the like is adhered to the rear surface of theground conductor part 100a of the metal plate 100, which is bent asshown in FIG. 5, by solder or the like. Thereafter, the metal plate 100with the heat sink 112 is encapsulated in molded plastic to form thepackage body 110b. In FIG. 5, the lid 120 is omitted.

According to the second embodiment of the present invention, since theheat sink 112 is present directly under the ground conductor 100a onwhich a microwave IC chip (not shown) is disposed, heat generated in themicrowave IC chip is effectively radiated through the heat sink,providing a surface mountable package suitable for a high powermicrowave IC chip.

FIG. 6 is a perspective view for explaining a microwave IC package inaccordance with a third embodiment of the present invention. In thisthird embodiment, a lid 130 for shielding the IC chip 1 is screwed tothe package body 110c.

More specifically, the metal plate 100 includes flanges 31 and 32upwardly bent with respect to the plane surface of the metal plate, andholes 31a and 32a are formed through the flanges 31 and 32,respectively. A lid 130 comprises a plane part 131 and flanges 132 and133 downwardly bent with respect to the plane part 131. Holes 132a and133a through the flanges 132 and 133 are located at positionscorresponding to the holes 31a and 32a of the flanges 31 and 32 of thepackage body 110c, respectively.

In fabrication, the microwave IC chip 1 is disposed on the metal plate100 and encapsulated in a molded plastic to form the dielectricsubstrate 111. Then, the lid 130 is put on the substrate 111, and theflanges 132 and 133 of the lid is fastened to the flanges 31 and 32 ofthe metal plate 100 with bolts 33 and nuts 34.

According to the third embodiment of the present invention, in additionto the effects of the first embodiment, the lid 130 is easily fixed ontothe package body with bolts and nuts.

FIGS. 7 and 8 are perspective views for explaining a microwave ICpackage in accordance with a fourth embodiment of the present invention.In this fourth embodiment, a package body 114a comprises a conductivesubstrate 114 on which the microwave IC chip 1 is disposed and groundedand input and output side transmission lines 50 and 60 for connectingthe microwave IC chip 1 to microwave transmission lines 410 and 420 on apackage substrate 401.

The grounding conductive substrate 114 comprises a metal, such as analloy of copper and tungsten, Kovar, or the like, onto which Au isplated. The input side transmission line 50 has a conventionalmicrostrip line structure in which a strip signal conductor is disposedon a dielectric that contacts a ground conductor. More specifically, thetransmission line 50 comprises an upper microstrip transmission linepart 50c, a lower microstrip transmission line part 50a, and anintermediate microstrip transmission line part 50b. The upper microstriptransmission line part 50c is disposed on the front surface of theconductive substrate 114 where the microwave IC chip 1 is to bedisposed. The lower microstrip transmission line part 50a is adjacent tothe conductive substrate 114, and the rear surface of the groundconductor thereof is level with the rear surface of the conductivesubstrate 114. The intermediate microstrip transmission line part 50a isdisposed on the side of the conductive substrate 114 and connects theupper microstrip transmission line part 50c to the lower microstriptransmission line part 50a.

The output side transmission line 60 comprises a microstrip transmissionline part 60c disposed on the front surface of the conductive substrate114, a lower microstrip transmission line part 60a whose rear surface islevel with the rear surface of the conductive substrate 114, and anintermediate microstrip transmission line part 60b (not shown)connecting the upper microstrip line 60c to the lower microstrip line50a.

The input side lower, intermediate and upper microstrip lines 50a, 50b,and 50c respectively comprise dielectric layers 53a, 53b, and 53ccomprising polyimide or the like, ground conductors 52a, 52b, and 52cdisposed on the rear surface of the dielectric layers, and strip signalconductors 51a, 51b, and 51c disposed on the front surface of thedielectric layers. The output side lower, intermediate and uppermicrostrip lines 60a, 60b, and 60c respectively comprise dielectriclayers 63a, 63b, and 63c, ground conductors 62a, 62b, and 62c, and stripsignal conductors 61a, 61b, and 61c. In addition, a lid 140 is put onthe package body 114 to cover the microwave IC chip 1. Solderingportions 114b and 114c are connected to the package substrate 401 withsolder, and thus the package 104 is adhered onto the package substrate401.

The input and output side transmission lines 50 and 60 are adhered tothe conductive substrate 114 with a conductive resin or the like. Whenpolyimide (εr =3.5) is used as the dielectric layer, the characteristicimpedance of each microstrip line can be set to 50Ω by making thethickness of the dielectric layer 50 microns and the width of the stripsignal conductor 95 microns.

Thus formed microwave IC package 104 is mounted on the package substrate401 whose surface is metallized a shown in FIG. 8. That is, it ismounted so that the input and output side lower microstrip lines 50a and60a may be laid on the signal supply side and signal transfer sidemicrostrip lines 410 and 420, respectively. At this time, the conductivesubstrate 114 and the ground conductors 52a and 62a are adhered to thesurface of the package substrate 401 with a conductive adhesive or thelike.

Then, the strip signal conductors 51a and 61a of the package areconnected to the strip signal conductors 411 and 421 of the packagesubstrate by bonding wires 12, respectively. The microstrip line 410 ofthe package substrate comprises a ground conductor 412 and a dielectriclayer 422, and the microstrip line 420 comprises a ground conductor 413and a dielectric layer 423.

According to the fourth embodiment of the present invention, themicrostrip transmission parts 50c and 60c disposed on the front surfaceof the conductive substrate 114 and the microstrip transmission parts50a and 60a whose rear surfaces are level with the rear surface of theconductive substrate 114 are connected by the intermediate microstriptransmission parts 50b and 60b disposed on the opposite side surfaces ofthe substrate 114, respectively. Therefore, the microwave transmissionpath from the package substrate 401 outside the package to the microwaveIC chip 1 inside the package is produced by the microstrip line, wherebya continuous transmission mode is maintained through the path from thepackage substrate 401 to the microwave IC chip 1. As the result, thereflection of high frequency signals caused by the mismatching ofcharacteristic impedances in the microwave transmission path issignificantly reduced.

Furthermore, in the package 104, the conductive substrate is used as thepackage body 114a, the heat radiating property of the package isimproved, and this package is suitable for a high power microwave ICchip.

As is evident from the foregoing description, according to the presentinvention, the upper coplanar line formed on the front surface of the ICchip substrate is connected to the lower coplanar line disposed on therear surface of the IC chip substrate, which is to be connected to thetransmission line on the package substrate, by an intermediate coplanarline penetrating through the IC chip substrate. Therefore, the microwavetransmission path from the package substrate outside the package to themicrowave IC chip inside the package is a coplanar transmission line, sothat a continuous transmission mode is maintained through the path fromthe package substrate to the microwave IC. As the result, reflection ofhigh frequency signals caused by the mismatching of characteristicimpedances in the microwave transmission line is significantly reduced.

In addition, since the lower coplanar line that can be connected to thecoplanar line on the package substrate is present on the rear surface ofthe package body, the microwave IC package is easily mounted on thepackage substrate with solder or the like.

In addition, a method of fabricating the IC chip substrate includespreparing a metal plate patterned in a shape corresponding to groundconductors and signal conductors of the coplanar transmission line,bending the metal plate, partially encapsulating the metal plate in amolded plastic, and removing unnecessary portions of the metal plate.Therefore, the IC chip substrate is easily formed by machining andplastic molding.

In addition, the radiating heat sink is disposed on the rear surface ofthe ground conductor on which the IC chip is disposed. Therefore, heatgenerated in the microwave IC chip is effectively radiated through theheat sink.

In addition, the metal plate includes flanges at both ends of the upperplane part of the bent metal plate, and holes in the flanges, whereby alid for shielding the microwave IC chip can be fastened to the flangeswith bolts and nuts using the holes. Therefore, the packaging of themicrowave IC chip is simplified.

Furthermore, according to the present invention, the upper microstripline on the front surface of the IC chip substrate is connected to thelower microstrip line disposed on the rear surface of the IC chipsubstrate, which is to be connected to the transmission line on thepackage substrate, by the intermediate microstrip line disposed on theside of the IC chip substrate. Therefore, the microwave transmissionpath from the package substrate outside the package to the microwave ICchip inside the package is produced by the microstrip transmission line,so that a continuous transmission mode is maintained through the pathfrom the package substrate to the microwave IC. As the result,reflection of high frequency signals caused by mismatching ofcharacteristic impedances in the microwave transmission line issignificantly reduced.

What is claimed is:
 1. A surface mountable microwave IC packagecomprising:a dielectric substrate having opposed front and rearsurfaces; a ground conductor disposed on the front surface of saiddielectric substrate to which a microwave IC chip may be mounted andgrounded; and a transmission line for connecting a microwave IC chipmounted on said ground conductor to a coplanar line on an externalpackage substrate outside the microwave IC package wherein saidtransmission line has a coplanar line structure including a signalconductor and a ground conductor disposed on said dielectric substrateand comprising: an upper coplanar line disposed on the front surface ofsaid dielectric substrate including said ground conductor; a lowercoplanar line disposed on the rear surface of said dielectric substrate;and an intermediate coplanar line penetrating through said dielectricsubstrate and connecting said upper coplanar line to said lower coplanarline.
 2. The microwave IC package of claim 1 wherein said dielectricsubstrate is formed by:preparing a metal plate as said conductivetransmission line for connecting the IC package to a package substrateincluding an H-shaped part, upper and lower I-shaped parts which aredisposed between and parallel to opposite side portions of said H-shapedpart, upper connecting parts connecting an upper end of said upperI-shaped part to upper ends of said H-shaped part, and lower connectingparts connecting a lower end of said lower I-shaped part to lower endsof said H-shaped part; bending said metal plate along two first linesparallel to a horizontal portion of said H-shaped part and opposite toeach other with said horizontal portion between, whereby said uppercoplanar line is formed; bending said metal plate along two second linesparallel to said horizontal portion of said H-shaped part and oppositeto each other with said horizontal portion between so that bent portionsare parallel to the plane surface of the metal plate, whereby saidintermediate coplanar line and said lower coplanar line are formed;partially encapsulating said metal plate in a plastic so that thesurface of said upper coplanar line where the microwave IC chip is to bedisposed and the rear surface of said lower coplanar line which is to beconnected to the package substrate are exposed; and removing said upperand lower connecting parts.
 3. The microwave IC package of claim 1wherein said transmission line for connecting the microwave IC packageto a package substrate includes an input side transmission linecomprising said upper, lower, and intermediate coplanar lines forconnection to a signal supply side coplanar line on a package substrateand an output side transmission line comprising said upper, lower, andintermediate coplanar lines for connection to a signal transfer sidecoplanar line on a package substrate.
 4. The microwave IC package ofclaim 1 comprising a lid for hermetically sealing and shielding amicrowave IC chip in said package.
 5. The microwave IC package of claim1 comprising a radiating heat sink contacting said ground conductor onwhich said IC chip is disposed.
 6. The microwave IC package of claim 2wherein said ground conductor includes flanges with holes and includinga lid for shielding the microwave IC chip and for fastening to saidflanges with bolts passing through the holes.
 7. A surface mountablemicrowave IC package comprising:a conductive substrate having a frontsurface on which a microwave IC chip may be mounted and grounded and anopposed rear surface; and a transmission line for connecting a microwaveIC chip mounted on said substrate to a microstrip transmission line on apackage substrate wherein said transmission line has a microstrip linestructure including a ground conductor, a dielectric substrate disposedon said ground conductor, and a strip signal conductor disposed on saidground conductor through said dielectric substrate and comprising: anupper microstrip line disposed on the front surface of said conductivesubstrate; a lower microstrip line disposed adjacent to said conductivesubstrate level with the rear surface of said conductive substrate; andan intermediate microstrip line disposed on said conductive substrateand connecting said upper microstrip line to said lower microstrip line.8. The microwave IC package of claim 7 wherein said transmission linefor connecting the IC chip to a package substrate includes an input sidetransmission line comprising said upper, lower, and intermediatemicrostrip lines for connection to a signal supply side microstrip lineon the package substrate and an output side transmission line comprisingsaid upper, lower, and intermediate microstrip lines for connection to asignal transfer side microstrip line on the package substrate.
 9. Themicrowave IC package of claim 8 comprising a lid hermetically sealed tosaid conductive substrate for sealing and shielding a microwave IC chipin said package.